System of control.



R. E. HELLMUND. SYSTEM OF CONTROL. APPLICATION FILED APR.29. 1915.

Patented Dec. 10, 1918.,

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ATTORNEY WITNESSES:

R. E. HELLMUND. SYSTEM OF CONTROL. APPLVICATION FILED APR. 29. I915.

3 SHEETS-SHEET 2- 2a 1; NWWWWWMAM INVENTOR" Rudolf Hal/mafia ATORNEY Patented Dec. 10, 1918.

R. Eu HELLMUND. SYSTEM OF CONTROL. APPLICATIQN FILED APR. 29. 1915.

Patented Dec. 10, 1918.

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WITNESSES UNITED STATES PATENT orrrcn.

BUDOLF IE. I-IELLMUND, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WESTING- HOUSE ELECTRIC A D MANUFACTURING GOMPAN Y, A CORPORATION OF PENN- SYLVANIA.

' SYSTEM OF CONTROL. 1,287,014. Specification of Letters Patent. P t t d D 10, 1913 Application filed April 29,1915. Serial No. 24,785. To all whom it may concern: the equalization of the load on the line by Be it known that I, RUDoLr E. HEILMUND, the simultaneous dropping of the frequency a subject of the Emperor of Germany, and and the voltage of the line. I have provided a resident of Pittsburgh, in the county of a system of motor control whereby all of the Allegheny and State of Pennsylvania, have above named connections and advantages 60 invented a new and useful Improvement in may be obtained in an extremely simple and Systems of Control, of which the following eifective manner.

is a specification. In the accompanying drawing, Figure 1 is y invention relates to control systems a diagrammatic view of a motor with its atfor alternating-current motors of the com tendant control circuits and auxiliary ap- 65 mutating type, and it has for one of its obparatus, illustrating one embodiment of my jects to provide means whereby a motor of invention; Fig. 2 is a chart showing the sethe character specified may be accelerated quence of switch operation in the control cirin a smooth and gradual manner with high cuit of Fig. 1 during the entire process of ac starting torque and subsequently be operated celeration; Figs. 3 to 10, inclusive, are sim- 70 at substantially uniform running speed, irplified diagrammatic views illustrating the respective of variations in the supply development of the connections in the sysvoltage. tern of Fig. l; and Fig. 11 is a diagrammatic Another object of my invention is to pro- 16W 0f a modification of the system shown vide means whereby a motor of the charac- 1n Fig. 1. 75

ter specified may, if coupled to a suitable An alternating-current motor 13 or" the mechanical load, be employed to regenerate compensated commutating type is provided and supply power to the source with a miniwith an armature 14, a main field winding mum amount of special auxiliary apparatus. 15 and a cross field winding 16. The motor Still another object of my invention is to 13 is supplied with alternating current from so provide a control system of the character a secondary winding 1? of a transformer 18 specified wherein the ratio of the number of provided with a primary winding 19 enercontrol switches to the number of acceleratgized from any suitable alternating current ing and running positions is lower than has line, such, for example, as a trolley wire 20. been customary hitherto and wherein many The connection between the motor 13 and 85 of the control switches carrybut a small porthe secondary winding 17 may be controlled tion of the load current and need therefore by suitable switches l, 2, 3 and 5 and a prebe of but small size. ventive reactance device 21.

In the operation of electric motors of the The main field winding 15 is energized, compensated, commutating, alternating-curnot only by current from the secondary ea. rent type it is desirable to have the apparawinding 17 but also by an auxiliary excittus connected either as a series, or as a repuling machine 22, preferably of the shortsion, motor during periods of acceleration circuited armature, phase-shifting type. in order that large starting torque and rela- Briefly stated, the machine 22 comprises an 40 tively small drain upon the line shall be armature 23 of the commutating type with produced. When the motor is running at its brushes short circuited, a mam field ful speed, however, it is preferable to so winding 24, and a cross field winding 25. connect it that it will have a shunt charac- Driving torque may be obtained from anyteristic in order that the power factor may suitable means, such, for example, as a vaat be readily controlled and that the speed may riable speed motor 26. Upon supplying the be maintained relatively constant when co main field winding 24 with alternating curnected to a source of variable Voltage. rent anddriving the armature 23, an alter- Furthermore,'the commutation is somewhat. nating current will be induced in the windbetter when operating with a shunt charing 25 which will be of the same frequency at acteristic, and the motor may be used for re as that supplied the winding 24- but will we geneiatien with but slight change in the difier thereiromin voltage, depending upon connections thereof. This last named tea the ratio between the number of turns in the ture is of great importance in electric railwindings and 25, and difiering thereway systems where regeneration be emfrom in phase, depending upon the position ployed for braking, for decelerating or for of the brushes of the armature 253 with rem secondary winding 28 on the transformer 18,

and the voltage applied to the mam field inducing winding 25 is preferab mented by a'small voltage derived winding 24 may be varied by suitable switches 9, 10, 11 and 12. The voltage supplied to the main field winding 15 by the ly supplefrom the secondary winding 28, as indicated at the right hand end thereof for phase control. The entire auxiliary exci ing circuit is controlled by a suitable switch 8.

The armature 14 may be connected or disconnected from the windings 15 and 16 by a switch 4, and the main field winding 15 may be shunted either by a resistance mem- 7 her 29, controlled by a suitable switch 6; or by a lower-resistance path controlled by the switch 6 and an additional switch 7.

Having thus described the arrangement of circuits for the control of the motor 13, the operation is as follows: Referring to the chart in Fig. 2, the accelerating positions are indicated in the left hand column and those of the accelerating positions, which are suitable for continuous running, are indicated by R in the next succeeding column. The remaining columns indicate the switches which are closed during each of the accelerating positions, as is well understood in the art. In spite of the advantages of a series or a repulsion connection, corresponding to a relatively steep speed-torque curve, for low-speed accelerating positions, I have found that a shunt connection, corresponding to a relatively fiat speed-torque curve, is best for the first speed because it permits one to definitely fix the strength of the main field to give the maximum short-circuit voltage under the brushes. This shunt operating connection is obtained, as indicated, by closing the switches 1, 2, 4, 5, 8, 9 and 12. See Fig. 3. The armature 14 is short circuited by the switches 2 and 4, and the cross field winding 16 is provided with a maximum excitation by being connected across the entire winding 17 The main field winding 15 is excited solely by the auxiliary machine 22 and the portion of the secondary winding28, giving a shunt operating characteristic to the motor 13. The excitation provided by the machine 22 is at a maximum because the main field winding 24 thereof is connected acrossthe maximum possible portion of the secondary winding 28 through switches 9 and 12.

In order to pass to the next running position, indicated as accelerating position number 4 on the chart, wherein the switches 1. 2, 5, 6 and 7 are closed, .as indicated in Fig. 4, and the main field winding 15 is excited solely by current induced in the armature 14 by the cross field windin 16, it is necessary, in order to avoid abrupt c anges in the speed,

relation to corresponding one speed-torque curve to another remotelyrelated curve, to transfer the excitation of the main field Winding 15 from the auxiliary source to the armature 14 in a smooth an radual manner. This result is obtained as indicated, by first closing the switch 6, connecting the resistance member 29 in shunt the field winding 15, allowing a small amount of current from the armature 14 to pass through the winding 15, then opening the switch 4 so rent flowing in the armature 14 is required to pass through the main field winding 15, and finally closing the switch 7 and opening the switch 8, whereby the resistance member 29 is eliminated from the circuit, the windings 14 and 15 are connected in series relation in a low-resistance loop, and the auxiliary excitation of the winding 15 is entirely removed.

While the motor 13 is thus operating solely with excitation from the source and with a series characteristic corresponding to a relatively steep speed-torque curve, the voltage produced by the machine 22 is lowered by reducing the excitation of the winding 24 by opening the switch 9 and closing the switch '10. i This operation would entail abrupt field changes in the field 15 were said machinedependent upon the machine 22 for excitation at all times but, by performing this operation when the machine 22 is disconnected from the winding 15, such abrupt field changes are avoided.

The next running position, indicated as the seventh accelerating notch corresponding to Fig. 5, has the same connections, corresponding to a relatively flat speedtorque curve, as does the first running position except that the voltage produced by the machine 22 is lower than in the earlier case. The transfer to these connections is made by reversing the aforementioned method of introducing the preventive resistance 29 as, will be readily apparent from the switch manipulation illustrated in connection with accelerating notches 5 and 6.

In passing to the next running position, found at the thirteenth accelerating notch corresponding to Fig. .6, wherein the connections are the'same as with the seventh accelerating position except that the voltage produced by the machine 22 is still lower, owing to the transfer of connection from the switch 10 to cycles of operation are gone through with as was followed between accelerating positions 1 and 7. It should be understood that the intermediate accelerating notches, corresponding to relatively steep speedtorque curves, are employed only for extremely short periods, as the connections 0 accelerating position 10, for .example, are

identical with those of accelerating position to a sudden transition from the switch 11, the same .cated at the thirteenth s, 6 and 7 4 and there would be a reversion to the speed of position a were the connections of position 10 maintaned for an appreciable period of time.

Between the two running positions indiand eighteenth accelerating positions, corresponding to Fig. 6 and to Fig. 7, respectively, an increase in speed is obtained by raising the voltage applied to the armature 14 through the closmg of the switch 3 and the opening of the switch 2. In the seventeenth acceleration position, the switches 2 and 3 are both closed but short circuiting of the attendant portion of the secondary winding 17 is prevented bv the action of the preventive-reactance evice 21. During the seventeenth, and all subsequent accelerating positions, the armaturel t is energized from the cross field winding 16 and also by direct-current iiow from the winding 17, thus producing the well lrnown doubly-fed connection for motors of this type. It will be noted that, by the establishment of an intermediate connection through the voltage 3, the voltage applied to the cross field winding 15 will be less than. has hitherto been the case, but the consequent reduction of current induced in the armature 14 will be compensated for by the additional direct flow from the winding 1?. During the sixteenth, seventeenth and eighteenth accelerating positions, the machine 13 is self-exciting with a series characteristic, and advantage is taken of this period for raising the voltage of he machine 22 to a maximum value through opening the switch 11 and closing the switch 9, so that, when the twentieth accelerating position is reached, connections are exactly the same as in the second accelerating position, with the exception that current flow has been introduced through the switch 3 and discontinued through the switch 2. From this point, acceleration is lowing the same cycles of operation as were employed in the lower accelerating stages, gradually reducing the voltage provided by the machine 22 and preventing abrupt changes in the excitation of the machine 13 through suitable manipulation of the switches and the preventive-resistance device 29. The simplified Figs. 8, 9 and 10, respectively representing conditions at the remaining running notches, namely, numbers 22, 26 and 30, thus correspond to Figs. 3, 5 and 6, respectively.

If desired, extremely gradual changes in the field 13 may be obtained by varying the speed of the machine 22 by controlling the speed of the driving motor thereof, as, for example, by a suitable rheostat connected in circuit with the auxiliary motor 26.

An extension of the above described method of control is shown in Fig. 11 wherein the main field winding of the phase consmall current, but it is produced by fol-v iary ource, and thereafter verter 22 has a substantially constant excitation from the source, and the control switches 9, 10 and 11 are transferred to the circuit of the driving motor 26, shown, in this case, as or" the repulsion type. The manipulation of the switches is the as in the circuit of F ig. l, the voltage of the machine 22 being raised by increasing the speed thereof rather than by increasing the main field excitation. A fly-wheel 27 on the shaft of the machine 22 prevents abrupt changes in the speed and, therefore, in the voltage of the exciting current supplied to the machine 13.

By the systems of connections shown, l am enabled t obtain eight running posi tions, with a large number of intermediate accelerating positions, by the use of but twelve switches, many of which carry but necessary for me to revert to the series operating connections when adjusting the voltage of the machine 22. 1' may, if desired. avoid this necessity by providing suitable preventive-resistance or reactive members at the switches 9, 1O

and 11, as is well known in the art. but to do so would entail additional switches with their attendant disadvantages.

While I have illustrated my invention in its preferred form, itwill be obvious to those skilled in the art that it is susceptible of various minor changes and modifications without departing from the spirit thereof, and I desire, therefore. that only such limitations shall be placed thereupon as are imposed by the rior art or are set forth in the appended claims.

l claim as my invention:

1. The method of accelerating an alternating-current commutator motor provided with both magnetizing and inducing-field windings, said motor being associated with a main source of alternating current and an auxiliary source of current, dephased with respect to said main source, and being provided with means for energizing said in ducing field winding directly from said main source, means for short-circuiting the armature winding, means for forming a closed circuit through said armature winding and said magnetizing-field winding, and means for jointly excitin said magnetizingfield winding from said main source and from adjustable portions of source, which comprises initially connecting said inducing-field winding across a pen tion of said main source, short-circuit-ing said armature winding, connecting said magnetizing-field windingto be jointly en ergized by a portion of said main source and by a relatively large portion of said auxilaccelerating said motor by decreasing the component of the magnetizing-field energization derived from said auxiliary source, closing a circuit from said auxiliary winding through said magwinding during transition adjustment of said component an adjacent portion of said source through said impedance device, means for inserting said magnetizing-field winding in said rmature-exciting circuit, and means for connecting said magnetizing-field winding to be energized jointly by a portion of said main'source and by said auxiliary source, which comprises initially connecting said inducing-field winding and armature windings to said main sourcethrough said'impedance device,'while including said magnetizing-field winding in said armature-exciting circuit, transferring said magnetizing-field winding t said joint exciting ,circuit with said dephased component at a relatively large value, and then decreasing the value of said dephased component.

3. The method of accelerating an alternating-current commutator motor provided with both magnetizing and inducing-field windings, said motor being associated with a main source of alternating current and an auxiliary source of current, dephased with respect to said main source, and being provided with means for energizing said inducing-field winding from a portion of said source, means for energizing the armature winding from an adjacent portion of said source, means for inserting said magnetizing-field winding in said armature-exciting circuit, and means for connecting said magnetizing-field winding to be energized jointly by a portion of said main source and by said auxiliary source, which comprises initially connecting said inducing-field winding and armature windings to said main source while including said magnetizing field winding in said armature-exciting circuit, transferring said magnetizing-field winding to said joint exciting circuit with said dephased component at a relatively large value, and then decreasing the value of said dephased component.

4. The method of accelerating an alternat ing-current commutator motor provided with both magnetizing and inducing-field windings, said motor being associated with a main source of alternating current and an auxiliary source of current, dephased with respect to said main source, and being prowindings, said motor vided with'means for ener izing said inducing-field winding directly om a ma or or a minor portion of saidmain source, means for short-circuiting the armature winding means for connecting said armature winding across a portion of said main source an means for jointly exciting said magnetizingfield winding from said main source and from adjustable portions of said auxiliary source whi h comprises initially connecting said inducing-field winding across a portion of said main source, short-circuiting saidarmature winding, connecting said magnetizing-field winding to be jointly energized by a portion of said main source and by a relatively large portion of said auxiliary source, accelerating said motor by decreasing said dephased component ofthe magnetizing field energization,. transferring to a connection wherein the armature and inducingfield windings are bothconnected across portions of said main source and said magnetizing-field winding is energized by said joint excitation with the dephased component at a maximum, and thereafter decreasing said idephased component of the magnetizing-field excitation.

5. The method of accelerating an alternating-current commutator motor provided with both magnetizing and inducing-field being associated with a main source of alternating current and an auxiliary source of current, dephased with respect to said main source, and being provided with means for energizing said inducing-field winding directly from a majoror a minor portion of said main source, including an im edance device in series with said inducingeld winding when connected across the minor portion of. said source,

means for short-circuiting the armature winding, means for connecting said armature winding across a portion of said main source through said impedance device, and means for jointly exciting said magnetizing-v field winding from said main source and from adjustable portions of said auxiliary source which comprises initially connecting said inducing-field winding across a portlon of said main source, short-circuiting said armature winding, connecting said magnetizing-field winding to be jointly energized by a portion of said main source and relatively large portion of said auxiliary source, accelerating said'motor by decreasing said dephased component of the magnetizing field energization, transferring to a' connection wherein the armature and inducing-field windings are both connected across portions of said main source through said impedance device and said magnetizing-field winding is energized by said joint excitation with the dephased component at a maximum, and thereafter decreasing said dono I connecting said or a minor portion source, means for short-circultin the armature Winding, means for includlng, said magnete portions of said auxiliary source which comprises initially inducingfield Winding across a portion of said main source, shortcircuiting said armature Winding, connect- 'd magnetizing field Windin jointly energized by a portion of said-main source and by a relatively large portion of said auxiliary source, accelerating said n10- tor by decreasing said of the magnetizing field energization, in-

a connection w erein the armature and inducing-field Windin s are both connected main source and stud magnetizing-field winding is energized by said joint excitation with the dephased component at a maxiload, again connecting th across portions of sald mum, and thereafter decreasing said dophased component of the magnetizing-field excitation.

7. The method of acceleratingan alternating-current commutator motor having both magnetizin and inducing field Windings in conjunction vvith a main source of shunt characteristic, excitlng said magnetizing field Winding in accordance with the mointermediate operating conditions, and gradually decreasing the component of the magnetizing-field-winding energization derived from said auxiliary source.

8. The method of operating an electric motor of the commutator type having a magnetizing field winding in conjunction .With a main source of ener y and an auxiliary source of current Whic comprises connectin said auxiliary source to said magneteld Winding together with the main source so as to produce a relatively flat speed-torque characteristic, subsequently excitin said magnetizing field stantial e main and the sources in circuit, and then gradually varying the magnetizing-field energization derived from saidauxiliary source.

11 testimony whereof, I have hereunto auxiliary subscribed myname this 23rd day of April 1915.

RUDOLF E. 

